Nowadays ansible uses a sort-of 'smart' method by default, where it first tries to use sftp, and if that fails, falls back to scp. See https://docs.ansible.com/ansible/latest/plugins/connection/s...

So if the server is compromised, it can fail the sftp in a suitable way?

But its another matter if ansible's scp client is vulnerable to this.

So if anyone is curious, the way to prevent this is:

scp_if_ssh = false